Method and apparatus for treating cardiac arrhythmia

ABSTRACT

An implantable system for the defibrillation or cardioversion of the atria and the ventricles of a patient&#39;s heart comprises: a first catheter configured for positioning in the right ventricle of the heart; a second catheter configured for positioning through the coronary sinus ostium and in the coronary sinus of the heart, with the first and second catheters together carrying at least three defibrillation electrodes; a power supply; and a control circuit operatively associated with the power supply and the electrodes. The control circuit is configured for delivering an atrial defibrillation pulse through at least two of the electrodes, or a ventricular defibrillation pulse through at least two of the electrodes.

This application is a continuation of U.S. patent application Ser No.09/393,857 filed Sep. 9, 1999, and now U.S. Pat. No. 6,122,553, which isa division of U.S. patent application Ser. No. 08/868,095, filed Jun. 3,1997, now issued as U.S. Pat. No. 5,978,704.

FIELD OF THE INVENTION

The present invention relates to methods and apparatus for treatingcardiac arrhythmia, and particularly relates to an implantable apparatusthat can treat both atrial and ventricular arrythmia with theimplantation of two transvenous leads.

BACKGROUND OF THE INVENTION

Atrial fibrillation is one of the most common cardiac arrhythmia. Healthconsequences associated with atrial fibrillation include decreasedcardiac output, less regular ventricular rhythm, the formation of bloodclots in the atrial appendages, and an increased incidence of stroke.While some drugs are available for the treatment of atrial fibrillation,they have a number of side effects which reduce their therapeuticutility.

Unlike patients afflicted with ventricular fibrillation, patientsafflicted with atrial fibrillation are conscious. The pain associatedwith the administration of the defibrillation shock can be severe, andthere is a need for means of carrying out atrial defibrillation in amanner that is less painful to the patient being treated. One means forreducing the pain associated with atrial defibrillation is to administermultiple shocks, but the administration of multiple shocks typicallyrequires the implantation of additional electrodes.

For ventricular fibrillation, the patient is generally unconscious, thecondition is life threatening, and the pain associated with shock is notan issue. It is, however, desirable to reduce the shock strengthadministered so that the size of the implantable device can be reduced,or to administer shocks in a manner that will decrease the likelihood ofrecurrence of fibrillation. To meet these objects, it is desirable toadminister multiple shocks. Again, the administration of multiple shocksrequires the implantation of additional electrodes.

Numerous patients are afflicted with both ventricular and atrialarrhythmias. For such patients, it would be exceedingly desirable toprovide a single device that can carry out both atrial and ventriculardefibrillation with minimum shock strength, and with minimal surgicalintervention.

In view of the foregoing, a first object of the invention is to providean implantable system for treating cardiac arrhythmia that does notrequire invasion of the chest cavity for the placement of epicardialelectrodes.

A second object of the invention is to provide an implantablecardioversion system wherein the probability of successful cardioversionon administration of the first cardioversion pulse is enhanced,particularly in the case of ventricular fibrillation.

A third object of the invention is to provide an implantable system fortreating cardiac arrhythmia that enables reduction of cardioversion, andparticularly defibrillation, shock strength.

A fourth object of the present invention is to provide methods andapparatus for carrying out atrial defibrillation that will reduce thepain associated therewith.

A fifth object of the present invention is to provide methods andapparatus for carrying out atrial defibrillation that will reliablytreat atrial fibrillation.

A sixth object of the present invention is to provide methods andapparatus for treating atrial fibrillation that minimizes the extent ofthe surgical intervention involved in implanting the necessarydefibrillation electrodes, and minimizes the complexity involved inimplanting the necessary defibrillation electrodes.

SUMMARY OF THE INVENTION

The foregoing and other objects and aspects of the present invention aredescribed in greater detail in the drawings herein and the specificationset forth below.

A first aspect of the present invention is an implantable system for thedefibrillation or cardioversion of the atria and the ventricles of apatient's heart. The system comprises: a first catheter configured forpositioning in the right ventricle of the heart; a second catheterconfigured for positioning through the coronary sinus ostium and in thecoronary sinus of the heart, with the first and second catheterstogether carrying at least three defibrillation electrodes; a powersupply; and a control circuit operatively associated with the powersupply and the electrodes. The control circuit is configured fordelivering an atrial defibrillation pulse through at least two of theelectrodes, or a ventricular defibrillation pulse through at least twoof the electrodes.

A second aspect of the present invention is an implantable system forthe defibrillation or cardioversion of the atria and the ventricles of apatient's heart. The system comprises: a first catheter configured forpositioning in the right ventricle of the heart; a second catheterconfigured for positioning through the coronary sinus ostium and in thecoronary sinus of the heart, with the first and second catheterstogether carrying at least three defibrillation electrodes; a powersupply; and a control circuit operatively associated with the powersupply and the electrodes. The control circuit is configured fordelivering an atrial defibrillation pulse through at least two of theelectrodes, or a ventricular defibrillation pulse through at least twoof the electrodes. The system includes a first and second pair of atrialdefibrillation electrodes operatively associated with the controlcircuit and power supply, with the first pair of atrial defibrillationelectrodes configured for delivering an atrial defibrillation pulsealong a first current pathway and the second pair of atrialdefibrillation electrodes configured for delivering a seconddefibrillation pulse along a second current pathway that is differentfrom the first current pathway, and wherein the control circuit isconfigured for delivering an atrial defibrillation shock comprising insequence the first and second atrial defibrillation pulses. Preferably,the system also includes a first and second pair of ventriculardefibrillation electrodes operatively associated with the controlcircuit and the power supply, with the first pair of ventriculardefibrillation electrodes configured for delivering a first ventriculardefibrillation pulse along a first current pathway and the second pairof ventricular defibrillation electrodes configured for delivering asecond defibrillation pulse along a second current pathway that isdifferent from the first current pathway, and wherein the controlcircuit is configured for delivering a ventricular defibrillation shockcomprising in sequence the first and second ventricular defibrillationpulses.

A third aspect of the present invention is an implantable system for thedefibrillation or cardioversion of the atria and the ventricles of apatient's heart. The system comprises: a first catheter configured forpositioning in the right ventricle of the heart; a second catheterconfigured for positioning through the coronary sinus ostium and in thecoronary sinus of the heart; with the first and second catheterscarrying at least three defibrillation electrodes, with the systemincluding a plurality of primary electrodes configured for delivering aventricular defibrillation pulse along a predetermined current pathwayin a first portion of the heart, the current pathway defining a weakfield area in a second portion of the heart, and with the defibrillationelectrodes further including at least one auxiliary electrode configuredfor delivering an auxiliary pulse to the weak field area, with at leastone auxiliary electrode configured for positioning through the coronarysinus and in a vein on the surface of the left ventricle of the heart; apower supply; and a control circuit operatively associated with thepower supply and the electrodes. The control circuit is configured fordelivering an atrial defibrillation pulse through at least two of theelectrodes, or a cardioversion sequence comprising a monophasicauxiliary pulse through the auxiliary electrode and a biphasicdefibrillation pulse through the primary electrodes. Preferably, thesystem also includes a first and second pair of atrial defibrillationelectrodes, with the first pair of atrial defibrillation electrodesconfigured for delivering an atrial defibrillation pulse along a firstcurrent pathway and the second pair of atrial defibrillation electrodesconfigured for delivering a second defibrillation pulse along a secondcurrent pathway that is different from the first current pathway, andwherein the control circuit is configured for delivering an atrialdefibrillation shock comprising in sequence the first and second atrialdefibrillation pulses.

A fourth aspect of the present invention is a transvenous catheter forinsertion into the heart of a patient, the catheter suitable for use incombination with a combination atrial and ventricular defibrillator. Thecatheter comprises an elongate lead flexibly configured for insertiondown the superior vena cava of the heart, into the right atrium, throughthe opening of the coronary sinus, through the proximal and distalcoronary sinus, and into a coronary vein on the surface of the leftventricle of the heart to achieve an operable configuration therein; afirst defibrillation electrode connected to the lead; a seconddefibrillation electrode connected to the lead at a position distal tothe first defibrillation electrode; and a third defibrillation electrodeconnected to the lead at a position distal to the second defibrillationelectrode. The first, second, and third defibrillation electrodes spacedapart on the lead so that, when the catheter is in the operableconfiguration, the first defibrillation electrode is positioned in theproximal coronary sinus of the heart, the second defibrillationelectrode is positioned in the distal coronary sinus or great cardiacvein of the heart, and the third defibrillation electrode is positionedin a coronary vein on the surface of the left ventricle of the heart.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a preferred set of electrode placements in anapparatus for carrying out the present invention;

FIG. 2 schematically illustrates control circuitry employed in anapparatus of the present invention;

FIG. 3 illustrates a biphasic waveform that may be used to carry outatrial or ventricular defibrillation in accordance with the presentinvention;

FIG. 4 illustrates first and second biphasic waveforms that may be usedto carry out atrial or ventricular defibrillation along two currentpathways in accordance with the present invention; and

FIG. 5 illustrates a first auxiliary waveform and a second biphasicwaveform that may be used to carry out atrial or ventriculardefibrillation along two current pathways in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention may be used to treat all forms of cardiactachyarrhythmias, including atrial and ventricular fibrillation, withdefibrillation (including cardioversion) shocks or pulses. The treatmentof polymorphic ventricular tachycardia, monomorphic ventriculartachycardia, ventricular fibrillation, and atrial fibrillation areparticularly preferred.

Anatomically, the heart includes a fibrous skeleton, valves, the trunksof the aorta, the pulmonary artery, and the muscle masses of the cardiacchambers (i.e., right and left atria and right and left ventricles). Theschematically illustrated portions of the heart 30 illustrated in FIG. 1includes the right ventricle “RV” 32, the left ventricle “LA” 34, theright atrium “RA” 36, the left atrium “LA” 38, the superior vena cava48, the coronary sinus “CS” 42, the great cardiac vein 44, the leftpulmonary artery 45, and the coronary sinus ostium or “os” 40.

The driving force for the flow of blood in the heart comes from theactive contraction of the cardiac muscle. This contraction can bedetected as an electrical signal. The cardiac contraction is triggeredby electrical impulses traveling in a wave propagation pattern whichbegins at the cells of the SA node and the surrounding atrial myocardialfibers, and then traveling into the atria and subsequently passingthrough the AV node and, after a slight delay, into the ventricles.

The beginning of a cardiac cycle is initiated by a P wave, which isnormally a small positive wave in the body surface electrocardiogram.The P wave induces depolarization of the atria of the heart. The P waveis followed by a cardiac cycle portion which is substantially constantwith a time constant on the order of 120 milliseconds (“ms”).

The “QRS complex” of the cardiac cycle occurs after the substantiallyconstant portion. The dominating feature of the QRS complex is the Rwave which is a rapid positive or negative deflection. The R wavegenerally has an amplitude greater than any other wave of the cardiaccycle, and has a spiked shape of relatively short duration with a sharprise, a peak amplitude, and a sharp decline. The R wave is thedepolarization of the ventricles and therefore, as used herein, the term“ventricle activations” denotes R waves of the cardiac cycle. The QRScomplex is completed by the S wave, which is typically a smalldeflection that returns the cardiac signal to baseline. Following the Swave, the T wave occurs after a delay of about 250 ms. The T wave isrelatively long in duration (e.g., about 150 ms). The cardiac cyclebetween the S wave and the T wave is commonly referred to as the STsegment. The T wave is a sensitive part of the cardiac cycle, duringwhich an atrial defibrillation shock is to be avoided, in order toreduce the possibility of an induced (and often fatal) ventricularfibrillation. The next cardiac cycle begins with the next P wave. Thetypical duration of a complete cardiac cycle is on the order of about800 ms.

Various embodiments of the present invention can be illustrated withreference to FIG. 1. The defibrillator 10 of FIG. 1 includes animplantable housing 13 that contains a hermetically sealed electroniccircuit 15 (see FIG. 2). The housing optionally, but preferably,includes an electrode comprising an active external portion 16 of thehousing, with the housing 13 preferably implanted in the left thoracicregion of the patient (e.g., subcutaneously, in the left pectoralregion) in accordance with known techniques as described in G. Bardy,U.S. Pat. No. 5,292,338. The system includes a first catheter 20 and asecond catheter 21, both of which are insertable into the heart(typically through the superior or inferior vena cava) without the needfor surgical incision into the heart. The term “catheter” as used hereinincludes “stylet” and is also used interchangeably with the term “lead”.Each of the catheters 20, 21 contains electrode leads wires 20 a, 20 b,20 c, 21 d, 21 e, and 21 f, respectively, with the small case letterdesignation corresponding to the large-case letter designation for thedefibrillation electrode to which each lead wire is electricallyconnected.

As illustrated in FIG. 1, the catheter 20 includes an electrode A; 50that resides in the right atrium (the term “right atrium” hereinincluding the superior vena cava and innominate vein), an electrode B;51 positioned in the right ventricle (preferably in the rightventricular apex), and an electrode C; 52 positioned within the leftpulmonary artery (the term “left pulmonary artery” herein includes themain pulmonary artery and the right ventricular outflow tract).

The second catheter 21 includes, from proximal to distal, a firstelectrode D; 53 positioned in the proximal coronary sinus, adjacent thecoronary sinus ostium or “os” 40; a second electrode E; 54 positioned inthe distal coronary sinus (preferably as far distal in the coronarysinus as possible) (the term “distal coronary sinus” herein includes thegreat cardiac vein); and a third electrode F; 55 at or adjacent the tipof the catheter in a coronary vein on the surface (preferably theposterolateral surface) of the left ventricle (e.g., in thelateral-apical left ventricular free wall). The position of electrode Fmay be achieved by first engaging the coronary sinus with a guidingcatheter through which a conventional guidewire is passed. The tip ofthe torqueable guidewire is advanced under fluoroscopic guidance to thedesired location. The lead 21 on which electrode F is mounted passesover the guidewire to the proper location. The guidewire is withdrawnand electrode F is incorporated into the defibrillation lead system.

Electrode A, 50 may optionally be positioned on lead 21 as electrode 50and retain the same operable positions described above as whenpositioned on lead 20.

The active external portion of the housing 16 serves as an optionalseventh electrode G, which may be used for either atrial or ventriculardefibrillation.

The electrodes described in FIG. 1 and the specification above may, forconvenience, be designated by the most adjacent structure. Thesestructures are: the right atrium (RA), right ventricle (RV), pulmonaryartery (PA), coronary sinus ostium (OS), distal coronary sinus (CS), andleft ventricle (LV). Thus, when applied to electrodes the electrodes ofFIG. 1:

RA means electrode A, 50;

RV means electrode B, 51;

PA means electrode C, 52;

OS means electrode D, 53;

CS means electrode E, 54; and

LV means electrode F, 55.

FIG. 2 illustrates one example of an implantable housing 13 containingan electronic circuit 15, which includes one or more amplifiers (notshown) for amplifying sensed cardiac signals. The amplified signals areanalyzed by a atrial and ventricular fibrillation detector 70 whichdetermines if ventricular fibrillation (or other arrhythmia, dependingon the specific treatment for which the device is configured) ispresent. The detector 70 may be one of several known to those skilled inthe art. As illustrated, a sensing signal may be provided by theelectrode A 50, it will be appreciated by those of skill in the art thatthe sensing electrode may also be a plurality of sensing electrodes witha plurality of signals, such as bipolar configurations, and may also beelectrodes that are positioned in alternate cardiac areas as is known inthe art, such as for example, the CS. In this situation, the input lineto the detector may be a plurality of lines which if providing onlysensing will provide an input to the detector.

Ventricular sensing for timing the shocks for atrial defibrillation maybe performed from the RV and/or LV electrodes.

The defibrillation electrodes may alternately be configured to sensecardiac cycles, or may have smaller sensing electrodes placed adjacentthereto and thereby provide input to the electronics package as well asprovide a predetermined stimulation shock output to predeterminedcardiac areas as directed by the controller.

The electronic circuit 15 also includes a cardiac cycle monitor(“synchronization monitor 72”) for providing synchronization informationto the controller 74. As discussed below, the synchronization istypically provided by sensing cardiac activity in the RV, but may alsoinclude other sensing electrodes which can be combined with thedefibrillation electrodes or employed separately to provide additionalassurance that defibrillation shock pulses are not delivered duringsensitive portions of the cardiac cycle so as to reduce the possibilityof inducing ventricular fibrillation.

Upon a signal from the detector 70, the controller 74, in turn, signalsa capacitor charging circuit 76 which then charges the storage capacitor78 to a predetermined voltage, typically from a battery source (notshown). The storage capacitor is typically 20 to 400 microfarads insize, and may be a single capacitor or a capacitor network (further, asdiscussed below, separate pulses can be driven by the same or differentcapacitors). The discharge of the capacitor is controlled by thecontroller 74 and/or a discharge circuit 80. The controller, based oninformation from the synchronization monitor 72, typically allows ordirects the preselected shock pulse to be relayed to either a dischargecircuit for further processing (i.e., to further shape the waveformsignal, time the pulse, etc.) or directly to a switch. The controllermay also control the proper selection of the predetermineddefibrillation electrode pair(s), where multiple defibrillationelectrodes are used, to direct the switch to electrically activate adesired electrode pair to align the predetermined electric shock pulsepathway through which the shock pulse is provided. As an alternative toa detector, the defibrillation pulses may be triggered by an externalsignal administered by a physician, with the physician monitoring thepatient for the appropriate time of administration.

Numerous configurations of capacitor and control circuitry may beemployed. The power supply may include a single capacitor, and thecontrol circuit may be configured so that both the auxiliary pulse andthe defibrillation pulse are generated by the discharge of the singlecapacitor. The power supply may include a first and second capacitor,with the control circuit configured so that the auxiliary pulse isgenerated by the discharge of the first capacitor and the defibrillationpulse is generated by the discharge of the second capacitor. In stillanother embodiment, the power supply includes a first and secondcapacitor, and the control circuit may be configured so that theauxiliary pulse is generated by the discharge (simultaneous orsequential) of both the first and second capacitors, and thedefibrillation pulse likewise generated by the discharge of the firstand second capacitors.

As illustrated by Table 1 below, numerous different combinations ofelectrodes from those shown in FIG. 1 may be employed to carry ouratrial and ventricular defibrillation. In Table 1, polarity of electrodeis illustrated by the direction of the arrows, but polarity is notcritical and can be reversed. As will be seen from Table 1, acombination at:rial and ventricular defibrillator may employ some or allof the electrodes illustrated in FIG. 1, and numerous combinationsthereof.

TABLE 1 Electrode configurations. Ventricular Atrial DefibrillationDefibrillation  1 RA−>RV RA−>CS  2 RA−>RV PA−>OS  3 RA−>RV RA−>OS  4RA−>RV OS−>CS  5 RA−>RV CS−>PA  6* RA−>RV PA−>RA  7 PA−>LV RA−>CS  8PA−>LV PA−>OS  9 PA−>LV RA−>OS 10 PA−>LV OS−>CS 11 PA−>LV CS−>PA 12PA−>LV PA−>RA 13 RA−>LV RA−>CS 14 RA−>LV PA−>OS 15 RA−>LV RA−>OS 16RA−>LV OS−>CS 17 RA−>LV CS−>PA 18 RA−>LV PA−>RA 19 PA−>RV RA−>CS 20PA−>RV PA−>OS 21 PA−>RV RA−>OS 22 PA−>RV OS−>CS 23 PA−>RV CS−>PA  24*PA−>RV PA−>RA 25 RV−>LV RA−>CS 26 RV−>LV PA−>OS 27 RV−>LV RA−>CS 28RV−>LV OS−>CS 29 RV−>LV CS−>PA 30 RV−>LV PA−>RA

Note that configurations 6 and 24, marked by an asterisk, employCatheter A only.

Those skilled in the art will appreciate that still additional electrodecombinations are possible for both atrial and ventricular defibrillationby employing the “active can” electrode G, 16, as discussed in greaterdetail below. In addition, multiple electrodes can be electricallycoupled or “tied” together to form a single pole. For example, a shockcan be delivered from either the RV or LV as one pole to the PA and OStied together as the other pole.

Any suitable waveform may be used to carry out the present invention,including both monophasic and biphasic waveforms. Amplitude, polarity,and duration of waveforms are not critical and will be apparent to thoseskilled in the art, particularly in light of the further discussionbelow.

For example, FIG. 3 illustrates a biphasic reverse exponential waveformthat may be used to carry out atrial or ventricular defibrillation inaccordance with the present invention, with the waveform being betweentime a and time b.

In a preferred embodiment of the invention, both atrial and ventriculardefibrillation pulses are delivered along dual current pathways. Anycombination of pathways among those set forth in Table 1 above may beemployed. Particularly preferred current pathways employing theelectrode configurations of FIG. 1 are set forth in Table 2 below.

TABLE 2 Dual current pathway electrode configurations. VentricularAtrial Defibrillation Defibrillation Pulse 1 Pulse 2 Pulse 1 Pulse 2 1RV−>RA LV−>PA LV−>RA RV−>PA 2 RV−>RA LV−>PA LV−>PA RV−>RA 3 RV−>PALV−>RA LV−>RA RV−>PA 4 RV−>PA LV−>RA LV−>RA RV−>RA 5 RV−>RA LV−>PARA−>CS PA−>OS 6 RV−>PA LV−>RA RA−>CS PA−>OS

As in Table 1 above, polarity of electrodes is illustrated by thedirection of the arrows, but polarity is not critical and can bereversed. In addition in Table 2, the order of pulse 1 and pulse 2 maybe switched, both for atrial defibrillation and ventriculardefibrillation.

When dual current pathways are employed for the defibrillation shock,the waveform for each current pathway may be monophasic or biphasic. Forexample, FIG. 4 illustrates first and second reverse exponentialbiphasic waveforms that may be used to carry out 'atrial or ventriculardefibrillation along two current pathways in accordance with the presentinvention. The first waveform of FIG. 4 is represented between time aand time b; the second waveform of FIG. 4 is represented between time cand time d. The time between the first and second waveforms (the timefrom time b to time c), will be apparent to those skilled in the art,but is preferably from 0 to 100 or 500 milliseconds, and more preferablyfrom 0.1 to 50 milliseconds.

As noted above, in a preferred embodiment of the present invention, amonophasic auxiliary waveform is delivered to a weak field area that isdefined by the current pathway of the defibrillation waveform. FIG. 5illustrates a first auxiliary waveform (from time a to time b) and asecond reverse exponential biphasic waveform (from time c to time d)that may be used to carry out atrial or ventricular defibrillation alongtwo current pathways in accordance with the present invention.

A. ATRIAL DEFIBRILLATION.

In overview, an implantable system for the defibrillation of the atriaof a patient's heart comprises (a) a first pair of atrial defibrillationelectrodes configured for delivering a first atrial defibrillation pulsealong a first current pathway in the heart; (b) a pulse generatoroperatively associated with the first pair of atrial defibrillationelectrodes for delivering the first atrial defibrillation pulse; (c) asecond pair of atrial defibrillation electrodes configured fordelivering a second atrial defibrillation pulse along a second currentpathway in the heart, with the second current pathway different from thefirst current pathway; and (d) a pulse generator operatively associatedwith the second pair of atrial defibrillation electrodes forsequentially delivering the second atrial defibrillation pulse after thefirst defibrillation pulse. The electrode pairs may be placed in avariety of different locations, as long as different current pathwaysfor the first and second pulse are thereby achieved. A single electrodemay participate in more than one electrode pair, so that, for example,two current pathways are achieved through three defibrillationelectrodes. Additional electrodes may be tied together to one member ofan electrode pair to provide a single pole, if so desired, andadditional electrodes may be provided for following the first and secondshocks with additional shocks.

In one embodiment of the invention, the first pair of atrialdefibrillation electrodes comprises a defibrillation electrodepositioned in the right atrium or superior vena cava of the heart, and adefibrillation electrode positioned in the distal coronary sinus orgreat cardiac vein of the heart. The electrodes themselves may beconfigured for positioning in the indicated location. Numerousalternatives for the second pair of atrial defibrillation electrodesforming a second pathway are possible. For example, the second pair ofatrial defibrillation electrodes may comprise:

(A) a defibrillation electrode positioned in the proximal coronary sinusof the heart, and a defibrillation electrode positioned anterior to theleft atrium of the heart (e.g., in the left pulmonary artery or on theexternal surface of a device implanted subcutaneously in the leftthoracic region of the patient);

(B) a defibrillation electrode positioned in the left pulmonary arterythe heart, and a defibrillation electrode positioned in the rightventricle of the heart;

(C) a defibrillation electrode positioned in the distal coronary sinusor great cardiac vein of the heart, and a defibrillation electrodepositioned in the right ventricle of the heart;

(D) a defibrillation electrode positioned in the left pulmonary arteryof the heart, and a defibrillation electrode positioned in the rightatrium of the heart;

(E) a defibrillation electrode positioned in the left pulmonary arteryof the heart, and a defibrillation electrode positioned in the distalcoronary sinus or great cardiac vein of the heart (the electrodepositioned in the distal coronary sinus or great cardiac vein mayoptionally be tied together with an electrode positioned in the rightatrium as one pole);

(F) a defibrillation electrode positioned in the proximal coronary sinusof the heart, and a defibrillation electrode positioned in the rightatrium of the heart; or

(G) a defibrillation electrode positioned in the proximal coronary sinusof the heart, and a defibrillation electrode positioned in the distalcoronary sinus or great cardiac vein of the heart (the electrodepositioned in the distal coronary sinus or great cardiac vein mayoptionally be tied together with an electrode positioned in the rightatrium as one pole).

Again, the electrodes may be configured for positioning in the indicatedlocations, and numerous variations on the foregoing will be readilyapparent to those skilled in the art. For example, the firstdefibrillation pulse could be delivered by the second pair of electrodesindicated above, and the second defibrillation pulse could be deliveredby the first pair of electrodes indicated above (in which case theindicated second pair of electrodes serves as the “first pair” and theindicated first pair serves as the “second pair”). In addition, multipleelectrodes may be implanted to provide three, four, or five or moredifferent alternative electrode pairs and current paths, and theelectrode coupling to the pulse generator switched after implantation ofthe electrodes to optimize the electrode configuration for a particularpatient.

As noted above, the instant invention provides two separate shock pulsesto two separate current pathways determined by the electrode pairarrangement also as discussed above. Therefore, it will be appreciatedby those of skill in the art that the capacitor 78 may be a singlecapacitor or a bank of parallel capacitors sufficiently charged andsized to be able to provide at least two separate shock pulses topredetermined electrodes positioned in the heart. Additionally, thecapacitor 78 can be two or more separately charged capacitors (or bankof parallel capacitors) on separate lines to provide two separate andsequential shock pulses as controlled by the controller 74 and/or thedischarge circuit 80. However, it is preferred that the capacitor 78 bea relatively large capacitor for insuring sufficient charge and decayperiod (i.e., long time constant and low tilt) to provide sufficientenergy for two shock pulses. For example, a capacitor with capacitancein the range of 200-1000 μf or more, having an associated time constantin the range of 30 ms, would typically be charged to approximately100-200 volts and would deliver a V(peak) in a typical first waveform ofabout 50-100 volts leading edge. If additional shocks beyond two areadministered, then a larger capacitor may be employed. In thealternative wherein the electronic package employs a circuit to furthershape the waveform, the capacitor may be charged to a higher voltagerange (such as around 200 V).

In one embodiment of the invention, the pulse generator includes asingle capacitor 78, and the controller 74 includes a switch (e.g., acrosspoint switch) operatively associated with that capacitor. Theswitch is configured to provide a biphasic pulse (i.e., a first phase ofa pulse of a predetermined polarity followed by a second phase of apulse of reversed polarity) as the first atrial defibrillation pulse anda biphasic pulse as the second atrial defibrillation pulse.

The controller 74 delivers a preselected electrical pulse topredetermined electrode pairs through a switch 82 which is preferablyprogrammable. The capacitor charger 76, capacitor 78, controller 74,discharge circuit 80 and switch 82 thus form an electrical pulsegenerator. Therefore, it will be appreciated that in operation, inresponse to an input from the atrial fibrillation detector 70, thecontroller 74 controls the pulse generator to synchronize the deliveryof the timed pulse output to the proper electrode pair in accordancewith the cardiac cycle information received from the synchronizationmonitor 72 and the specific electrode configuration employed by thedevice. Further, when employing a biphasic waveform, it will beappreciated by those of skill in the art that the pulse generator alsoincludes a crosspoint switch to switch the polarity of the electrodepair for delivery of the second (inverted or negative) waveform phase.It is also preferable that the electronic package include areceiver/transmitter coupled to the internal controller 74 forcommunicating with an external controller. Thus the pulse regimen couldbe altered by external input to the controller to alter for example, thewaveform, the voltage, the electrode coupling, or even to retrieve datamonitoring data received and stored in memory about the number of atrialfibrillation episodes and the effectiveness of the shock level.

In one embodiment of the invention, the switch 82 is programmable (e.g.,by remote control such as by a radio signal) to alter the coupling ofthe pulse generator to the atrial defibrillation electrodes. Thisfeature is advantageously employed when multiple electrodes areimplanted so that the electrode pairs that deliver the first and secondatrial defibrillation pulses may be changed to optimize the techniquefor a particular patient.

The energy of the first atrial defibrillation pulse is preferably notgreater than 8 joules, more preferably not greater than 6 joules, stillmore preferably not greater than 4 joules, and most preferably notgreater than 2 joules. The energy of the second atrial defibrillationpulse is typically not greater than the energy of the firstdefibrillation pulse (although such a result is possible where a dualcapacitor design is employed), and is preferably not greater than 8joules, more preferably not greater than 6 joules, still more preferablynot greater than 4 joules, and most preferably not greater than 2joules. The second atrial defibrillation pulse preferably follows thefirst atrial defibrillation pulse by 0 to 500 milliseconds, and morepreferably follows the first atrial defibrillation pulse by 0 to 200milliseconds. In the alternative, the second atrial defibrillation pulsemay overlap the first atrial defibrillation pulse, for example by fromone fourth to three fourths of the total shock duration (the duration ofboth shocks in series). The duration of each shock may be, for example,from three to twenty milliseconds, with total shock duration being, forexample, from four and one half to forty milliseconds.

B. VENTRICULAR DEFIBRILLATION

One preferred embodiment of the foregoing apparatus is an implantablesystem for the defibrillation of the ventricles of the heart of apatient in need of such treatment. The system comprises a plurality ofprimary electrodes, at least one auxiliary electrode, a power supply,and a control circuit. The plurality of primary electrodes areconfigured for delivering a defibrillation pulse along a predeterminedcurrent pathway in a first portion of the heart, the current pathwaydefining a weak field area in a second portion of the heart. At leastone auxiliary electrode is configured for delivering an auxiliary pulseto the weak field area, with the at least one auxiliary electrodeconfigured for positioning through the coronary sinus and in a vein onthe surface of the left ventricle of the heart. The control circuit isoperatively associated with the primary electrodes, the at least oneauxiliary electrode, and the power supply, the control circuitconfigured for delivering a cardioversion sequence comprising amonophasic auxiliary pulse through the auxiliary electrode, followed bya biphasic defibrillation pulse through the primary electrodes, with thedefibrillation pulse delivered within 20 milliseconds after theauxiliary pulse, and with the first phase of the defibrillation pulse inopposite polarity to the auxiliary pulse.

The auxiliary pulse may be from 0.5 or 1 to 5 or 10 milliseconds induration, with a 2 millisecond pulse currently preferred. The timeinterval from the end of the auxiliary pulse to the leading edge of theprimary pulse may be from 1 or 2 milliseconds to 10, 15 or 20milliseconds, with a delay of about 5 milliseconds currently preferred.

The optimal auxiliary-to-primary interval may differ depending on thetype of rhythm or condition of the myocardial tissue at the time thetherapy is applied. Therefore, the control circuitry may also beconfigured to sense a characteristic of the cardiac rhythm (e.g., anactivation interval or a dynamical pattern of consecutive activationintervals) and then select an optimum auxiliary-to-primary shock timeinterval (e.g., from a look up table stored in a microprocessor memory).

In general, the control circuit is configured so that the auxiliarypulse is not more than 40% or 50% of the peak current and not more than20% or 30% of the delivered energy (in Joules) of the defibrillationpulse. In a preferred embodiment, the trailing edge voltage of theauxiliary pulse is approximately or about equal to the leading edgevoltage of the defibrillation pulse. Particular voltage, current, andenergy outputs will depend upon factors such as the condition of thetissue and the particular disorder being treated. In general, theauxiliary pulse may have a peak voltage of from 20 or 30 volts to 200 or250 volts, with a peak voltage range of 50 to 150 volts preferred. Theenergy of the auxiliary pulse may be from 0.01 or 0.05 to 1 or 2 Joules.The energy of the defibrillation pulse may be from 5 or 10 Joules to 30,40 or 50 Joules.

C. GENERAL

Systems as described above may be implanted in a patient by conventionalsurgical techniques, or techniques readily apparent to skilled surgeonsin light of the disclosure provided herein, to provide an implanteddefibrillation or cardioversion system.

Additional features can also be added to the invention without affectingthe function of the invention and result thereof. Such additionalfeatures include, but are not limited to, safety features such as noisesuppression or multiple wave monitoring devices (R and T), verificationchecking to reduce false positive, precardioversion warning, programmeddelayed intervention, bipolar configured sensing electrodes,intermittently activated defibrillation detector to reduce energydrain,. a switching unit to minimize lines from the pulse generator,etc.

Although the system has been described above as an implantable system,it will be appreciated by those of ordinary skill in the art that theinvention could also be incorporated into an external system whichemploys catheters to position the electrodes for a short time within apatient's heart.

The foregoing is illustrative of the present invention, and are not tobe construed as limiting thereof. The invention is defined by thefollowing claims, with equivalents of the claims to be included therein.

That which is claimed is:
 1. A method of delivering selective shockpulses to a patient's heart to induce the appropriate defibrillationthereof, comprising the steps of: inserting a plurality of spaced apartelectrodes into the natural lumens of the patient's heart such that thateach electrode resides in different locations therein, so that at leasta first atrial defibrillation shock pathway is defined by at least twoof said plurality of spaced apart electrodes and at least a firstventricular defibrillation shock pathway is defined by at least two ofsaid plurality of spaced apart electrodes; sensing cardiac signalsassociated with the cardiac activity of the patient's heart with atleast one of said plurality of spaced apart electrodes; detecting thepresence of atrial fibrillation based on said sensing step; detectingthe presence of ventricular fibrillation based on said sensing step;transmitting a first atrial defibrillation shock pulse to said firstatrial defibrillation shock pathway responsive to said first detectingstep, wherein the first atrial shock pulse exposing the patient to ashock pulse energy level of less than about 8 joules; and transmitting afirst ventricular defibrillation shock pulse to said first ventriculardefibrillation shock pathway responsive to said second detecting step.2. A method according to claim 1, wherein the plurality of electrodesdefine a second atrial defibrillation shock pathway different from thefirst atrial defibrillation shock pathway, the method further comprisingthe step of transmitting a second atrial shock pulse to the secondatrial defibrillation shock pathway responsive to said first detectingstep, the second atrial shock pulse exposing the patient to a shockpulse energy level which is less than about 8 joules.
 3. A methodaccording to claim 2, wherein said first and second atrialdefibrillation transmitting steps are performed sequentially.
 4. Amethod according to claim 3, wherein said first and second atrialdefibrillation transmitting steps are performed within about 0-500 ms ofthe other.
 5. A method according to claim 1, wherein the plurality ofelectrodes define a second ventricular defibrillation shock pathwaydifferent from the first ventricular defibrillation shock pathway, themethod further comprising the step of transmitting a second ventricularshock pulse to the second ventricular defibrillation shock pathwayresponsive to said second detecting step.
 6. A method according to claim5, wherein said first and second ventricular defibrillation transmittingsteps are performed sequentially.
 7. A method according to claim 6,wherein said first and second ventricular defibrillation transmittingsteps are performed within about 0-500 ms of the other.
 8. A methodaccording to claim 1, further comprising the step of generating theventricular and atrial shock pulses within the patient via animplantable housing operably associated with said plurality ofelectrodes.
 9. A method according to claim 8, wherein said sensing stepincludes the step of directing the sensed cardiac signals to acontroller located in the implantable housing.
 10. A method according toclaim 8, wherein said plurality of electrodes are positioned on twodifferent catheters, each catheter operably associated with the housing.11. A method according to claim 10, wherein said inserting step iscarried out such that a first electrode resides in the right atrium(RA), a second electrode resides in the right ventricle (RV), a thirdelectrode resides in the pulmonary artery (PA), a fourth electroderesides in the coronary sinus ostium (OS), a fifth electrode resides inthe distal coronary sinus (CS), and a sixth electrode resides in theleft ventricle (LV).
 12. A method according to claim 11, wherein theelectrode positioned in the left ventricle is positioned in a coronaryvein such that it resides on the surface of the left ventricle.
 13. Amethod according to claim 11, wherein the plurality of electrodes definea second atrial defibrillation shock pathway different from the firstatrial defibrillation shock pathway such that the second atrialdefibrillation shock pathway is defined by a different combination ofsaid plurality of spaced apart electrodes from the first atrialdefibrillation shock pathway, the method further comprising the step oftransmitting a second atrial shock pulse to the second atrialdefibrillation shock pathway responsive to said first detecting step,the second atrial shock pulse exposing the patient to a shock pulseenergy level which is less than about 8 joules.
 14. A method accordingto claim 13, wherein the plurality of electrodes define a secondventricular defibrillation shock pathway different from the firstventricular defibrillation shock pathway such that the secondventricular defibrillation pathway is defined by a different combinationof said plurality of spaced apart electrodes from the first ventriculardefibrillation pathway, the method further comprising the step oftransmitting a second ventricular shock pulse to the second ventriculardefibrillation shock pathway responsive to said second detecting step.15. A method according to claim 14, wherein one of said first and secondventricular defibrillation current pathways includes at least the secondelectrode in the RV on one pole and the first electrode in the RA on theother pole.
 16. A method according to claim 15, wherein the other one ofsaid first and second ventricular defibrillation current pathwaysincludes at least the sixth electrode in the LV on one pole and thethird electrode in the PA on the other pole.
 17. A method according toclaim 15, wherein the other one of said first and second ventriculardefibrillation current pathways includes at least the sixth electrode inthe LV on one pole and the first electrode in the RA on the other pole.18. A method according to claim 15, wherein one of said first and secondventricular defibrillation current pathways includes at least the secondelectrode in the RV on one pole and the third electrode in the PA on theother pole.
 19. A method according to claim 18, wherein the other one ofsaid first and second ventricular defibrillation current pathwaysincludes at least the sixth electrode in the LV on one pole and thefirst electrode in the RA on the other pole.
 20. A method according toclaim 14, wherein one of said first and second atrial defibrillationcurrent pathways includes at least the sixth electrode in the LV on onepole and the third electrode in the PA on the other pole, wherein one ofsaid first and second atrial defibrillation current pathways includes atleast the second electrode in the RV on one pole and the first electrodein the RA on the other pole, wherein one of said first and secondventricular defibrillation current pathways includes at least the secondelectrode in the RV on one pole and the first electrode in the RA on theother pole, and wherein the other one of said first and secondventricular defibrillation current pathways includes at least the sixthelectrode in the LV on one pole and the third electrode in the PA on theother pole.
 21. A method according to claim 14, wherein one of saidfirst and second atrial defibrillation current pathways includes atleast the sixth electrode in the LV on one pole and the third electrodein the PA on the other pole, wherein one of said first and second atrialdefibrillation current pathways includes at least the second electrodein the RV on one pole and the first electrode in the PA on the otherpole, wherein one of said first and second ventricular defibrillationcurrent pathways includes at least the second electrode in the RV on onepole and the third electrode in the PA on the other pole, and whereinthe other one of said first and second ventricular defibrillationcurrent pathways includes at least the sixth electrode in the LV on onepole and the first electrode in the RA on the other pole.
 22. A methodaccording to claim 14, wherein the first and second ventricular shockpulses are biphasic waveforms.
 23. A method according to claim 13,wherein one of said first and second atrial defibrillation currentpathways includes at least the sixth electrode in the LV on one pole andthe first electrode in the RA on the other pole.
 24. A method accordingto claim 23, wherein the other of one of said first and second atrialdefibrillation current pathways includes at least the second electrodein the RV on one pole and the third electrode in the PA on the otherpole.
 25. A method according to claim 23, wherein one of said first andsecond atrial defibrillation current pathways includes at least thesecond electrode in the RV on one pole and the first electrode in the RAon the other pole.
 26. A method according to claim 13, wherein one ofsaid first and second atrial defibrillation current pathways includes atleast the sixth electrode in the LV on one pole and the third electrodein the PA on the other pole.
 27. A method according to claim 26, whereinone of said first and second atrial defibrillation current pathwaysincludes at least the second electrode in the RV on one pole and thefirst electrode in the RA on the other pole.
 28. A method according toclaim 13, wherein one of said first and second atrial defibrillationcurrent pathways includes at least the sixth electrode in the LV on onepole and the third electrode in the PA on the other pole.
 29. A methodaccording to claim 28, wherein one of said first and second atrialdefibrillation current pathways includes at least the second electrodein the RV on one pole and the first electrode in the RA on the otherpole.
 30. A method according to claim 13, wherein one of said first andsecond atrial defibrillation current pathways includes at least thefirst electrode in the RA on one pole and the fifth electrode in the CSon the other pole.
 31. A method according to claim 30, wherein one ofsaid first and second atrial defibrillation current pathways includes atleast the third electrode in the PA on one pole and the fourth electrodein the OS on the other pole.
 32. A method according to claim 13, whereinthe first and second atrial shock pulses are biphasic waveforms.
 33. Amethod according to claim 10, wherein said inserting step is carried outsuch that a first electrode resides in the right atrium (RA), a secondelectrode resides in the right ventricle (RV), a third electrode residesin the pulmonary artery (PA), and fourth electrode resides in thecoronary sinus ostium (OS), a fifth electrode resides in the distalcoronary sinus (CS), and a sixth electrode resides in the left ventricle(LV).
 34. A method according to claim 33, further comprising a seventhelectrode defined by an active external portion of the implantablehousing.
 35. A method according to claim 10, further comprising the stepof: transmitting a second atrial shock pulse to a second atrialdefibrillation current pathway different from the first atrialdefibrillation current pathway responsive to said step of determiningthe presence of atrial fibrillation, wherein the second atrial shockpulse exposes the patient to a shock pulse energy level of less thanabout 8 joules, wherein the second atrial defibrillation current pathwayis defined by a different combination of said plurality of spaced apartelectrodes from the first atrial defibrillation current pathway; andtransmitting a second ventricular shock pulse to a second ventriculardefibrillation current pathway different from the first ventriculardefibrillation current pathway responsive to said step of determiningthe presence of ventricular fibrillation, wherein the second ventriculardefibrillation current pathway is defined by a different combination ofsaid plurality of spaced apart electrodes from the first ventriculardefibrillation current pathway.
 36. A method according to claim 35,further comprising the step of generating the ventricular and atrialshock pulses within the patient via an implantable housing operablyassociated with said plurality of electrodes, wherein said insertingstep is carried out such that a first electrode resides, at leastpartially, proximate the superior vena cava of the right atrium (SVCRA),a second electrode resides in the right ventricle (RV), a thirdelectrode resides in a coronary vein on the surface of the leftventricle (LV), and wherein said implantable housing has an active canwhich defines a fourth electrode.
 37. A method according to claim 36,wherein one of said first and second atrial defibrillation currentpathways includes at least the third electrode in the LV on one pole andthe first electrode in the SVCRA on the other pole.
 38. A methodaccording to claim 37, wherein the other one of said first and secondatrial defibrillation current pathways includes at least the secondelectrode in the RV on one pole and the first electrode in the SVCRA andthe fourth housing can electrode on the other opposing pole.
 39. Amethod according to claim 36, wherein said inserting step furtherpositions a fifth electrode in the distal coronary sinus (DCS).
 40. Amethod according to claim 39, wherein one of said first and secondatrial defibrillation current pathways includes at least the fifthelectrode in the DCS on one pole and the first electrode in the SVCRA onthe other pole.
 41. A method according to claim 40, wherein the otherone of said first and second atrial defibrillation current pathwaysincludes at least the second electrode in the RV on one pole and thefirst electrode in the SVCRA and the fourth housing can electrode on theother opposing pole.
 42. A method according to claim 36, wherein one ofsaid first and second ventricular defibrillation current pathwaysincludes at least the third electrode in the coronary vein in the LV onone pole and the first electrode in the SVCPA and the fourth housing canelectrode on the other opposing pole.
 43. A method according to claim42, wherein the other of said first and second ventriculardefibrillation current pathways includes the second electrode in the RVon one pole and the first electrode in the SVCRA and the fourth housingcan electrode on the other pole.
 44. A method according to claim 43,wherein the other one of said first and second ventriculardefibrillation current pathways includes at least the electrode in theLV on one pole and the electrode in the PA on the other pole.
 45. Amethod according to claim 36, wherein said atrial and ventricular shockpulses are biphasic waveforms.